The hippopotamus, whose hide alone can weigh half a
ton, is the third-largest living land mammal, after elephants
and white rhinos. It was considered a female deity of pregnancy
in ancient Egypt, but in modern times has been wiped out of that
country because of the damage it inflicts on crops. The hippo
continues to thrive in other parts of Africa.

Physical Characteristics
The hippo's proportions reflect its sedentary, amphibious
existence. Its plump and bulky body is set on short, stumpy
legs, with each foot having four toes. Although webbed, the toes
splay enough to distribute the weight evenly over each toe and
therefore adequately support the hippo on land.

With very thick skin, especially over the back and rump, the
grayish-brown body is almost completely hairless, with only a
few bristles around the mouth and the tip of the tail. The hippo
has neither sweat nor sebaceous glands but does have unique
glands that produce a viscous red fluid, leading to the myth
that hippos "sweat blood." The hippo relies on water or mud to
keep it cool, and the red fluid may have a similar function, but
it is often produced in copious amounts when the animal is
excited.

Habitat
Two hippo species are found in Africa. The large hippo, found in
East Africa, occurs south of the Sahara. This social,
group-living mammal is so numerous in some areas that "cropping"
schemes are used to control populations that have become larger
than the habitat can sustain. The other, much smaller (440 to
605 pounds) species of hippo is the pygmy hippopotamus (Choeropsis
liberiensis). Limited to very restricted ranges in West
Africa, it is a shy, solitary forest dweller, and now rare.

Behavior
The large hippo is an aggressive animal; old scars and fresh,
deep wounds are signs of daily fights that are accompanied by
much bellowing, neighing and snorting. Hippos have developed
some ritualized postures the huge open-mouthed "yawn" that
reveals formidable teeth is one of the most aggressive. With the
long, razor-sharp incisors and tusklike canines, the hippo is
well-armed and dangerous.

Hippos move easily in water, either swimming by kicking their
hind legs or walking on the bottom. They are well-adapted to
their aquatic life, with small ears, eyes and nostrils set at
the top of the head. These senses are so keen that even
submerged in water, the hippo is alert to its surroundings. By
closing its ears and nostrils, the adult can stay under water
for as long as six minutes.

Hippos have a flexible social system defined by hierarchy and
by feed and water conditions. Usually they are found in mixed
groups of about 15 individuals, but in periods of drought large
numbers are forced to congregate near limited pools of water.
This overcrowding disrupts the hierarchical system, resulting in
even higher levels of aggression, with the oldest and strongest
males most dominant. Hippos are unpredictable. If they are
encountered away from the safety of water, anything that gets
between them and their refuge may be bitten or trampled.

Diet
Amazingly agile for their bulk, hippos are good climbers and
often traverse rather steep banks each night to graze on grass.
They exit and enter the water at the same spots and graze for
four to five hours each night in loop patterns, covering one or
two miles, with extended forays up to five miles. Their modest
appetites are due to their sedentary life, which does not
require high outputs of energy.

Caring for the Young
A single young is born either on land or in shallow water. In
water, the mother helps the newborn to the surface, later
teaching it to swim. Newly born hippos are relatively small,
weighing from 55 to 120 pounds, and are protected by their
mothers, not only from crocodiles and lions but from male hippos
that, oddly enough, do not bother them on land but attack them
in water.

Young hippos can only stay under water for about half a
minute, but adults can stay submerged up to six minutes. Young
hippos can suckle under water by taking a deep breath, closing
their nostrils and ears and wrapping their tongue tightly around
the teat to suck. This procedure must be instinctive, because
newborns suckle the same way on land. A young hippo begins to
eat grass at 3 weeks, but its mother continues to suckle it for
about a year. Newborns often climb on their mothers' backs to
rest.

Predators
Compared to other animals, hippos are not very susceptible to
disease, so in suitable habitats, their numbers can increase
quickly. Their chief predators are people, who may hunt hippos
for their meat, hides and ivory teeth.

Did you know?

The name hippopotamus comes from the Greek "hippos,"
meaning horse, these animals were once called "river horses."
But the hippo is more closely related to the pig than the
horse.

Hippos spend most of their day in water close to shore
lying on their bellies. In areas undisturbed by people, hippos
lie on the shore in the morning sun.